1. Field of Invention
The present invention relates to annular core or barrel drilling. More particularly, this invention describes a method and apparatus for drilling, cracking, and withdrawing solid earth and rock cores.
2. Description of the Prior Art
Rotary core or barrel drilling is a well known and understood method of drilling holes by coring the earth. It involves the use of an annular drill bit, head or core barrel attached to conventional drill machinery which rotates and pushes the head or barrel downward into earth and rock. These drills core the ground such that, when the core barrel is withdrawn, barrel shaped core material is left within the bore hole. This core material is awkward and cumbersome to remove, particularly in the case of wide diameter cores. When drilling dense earth or rock, the core is left attached to the ground at its base requiring that it be freed prior to removal.
Apparatus and methods for grabbing and withdrawing material from well drill holes are well know and available in a variety of forms. Many spring loaded fishing tools and grappling devices have been described which are lowered into, or mounted within, drill stems and casings. These tools and devices, such as the apparatus described in U.S. Pat. No. 1,553,540 issued to Kurtz and U.S. Pat. No. 1,571,332 issued to Herminghausen, are suitable for extracting small articles and obstacles encountered or lost while drilling narrow-diameter deep well holes.
Devices for removing core materials from inside a drill casing, for purposes of sampling the core materials or otherwise, have also been described. U.S. Pat. No. 331,319 issued to Parker and U.S. Pat. No. 1,252,555 to Dodds describe apparatus which scoop or grapple core material while functioning from within the drill stem or casing.
All the above described apparatus and devices rely upon the drill stem or casing remaining in the drill hole for their operation. These devices are appropriate for use in narrow-diameter deep drill holes but may not be suitable or efficient for removing large diameter solid earth or rock cores. Such devices may be incapable of freeing solid earth and rock cores left attached to the ground at their base.
Large-diameter, shallow earth core drilling is commonly employed for digging dry wells, holes for building foundations, roadways and other infrastructure. A primary object of the present invention is to provide a means to free and remove solid cores left after barrel drilling, particularly in the case of wide-diameter cores composed of dense earth and rock material.
U.S. Pat. No. 1,730,705, issued to Wild, describes an apparatus having a plurality of opposed shovels for removing solid or loose core material. Wild's device is lowered into drilled core grooves after removal of the barrel drill. Relying substantially on gravity and mechanical lifting means, the forces available to break up and lift core material are limited. A further purpose of the present invention is to provide a method for removing large diameter solid earth or rock cores when great force is required in order to free and secure the core material for its withdrawal from the drill hole.